1. Field of the Invention
This invention relates to a thermally and acoustically insulating structure of the type including a plurality of glass sheets arranged to define air spaces therebetween, more particularly to improved structure which provides both high average acoustical transmission loss and anti-dewing effects, comprising means to make the air in the air spaces circulate therebetween to keep it dry, and means to keep the small spaced sheets away from each other thereby preventing the effect of the so-called Newton's rings.
2. Description of the Prior art
There are known hereto various types of thermally and acoustically insulating structure for use windows or doors. According to one conventional type of structure, there are three sheets of glass arranged to define relatively wide air spaces therebetween, the air spaces containing air drying agents. The structure is designed to insulate incoming sounds of particularly high frequency range and provide a thermal insulating effect. Another known type of structure has at least one relatively small air space between the two adjacent sheets which have the peripheral edges coated with adhesive, thereby absorbing incoming sounds therein. A further different type of construction includes three sheets of glass defining air spaces of a different width therebetween to cut off heat radiation therethrough. A four glass structure has two pairs of outer and inner glass sheets, the inner glass sheets being widely spaced by spacer means and containing an air drying agent in the space. The adjacent inner and outer sheets are less widely spaced and are held in that position by wrapper band. There are other similar types known which have two or more glass sheets spaced identically or differently . All of these known structures have disadvantages and problems. The first cited prior structure containing separate drying agents in the defined air spaces has no means to communicate with the two air spaces for circulating the air therebetween, thus making it necessary to install individual drying agents in the respective air spaces. It is however necessary to provide a very narrow air space between the sheets so as to increase the insulating effect on the incoming sounds of particularly low frequency range, and also to close the air space airtightly from the outside by means of sealant material. However, the above-cited structure and other structures, if the small air space is provided, are not capable of maintaining the air space in a dry condition because of the structural limitation. Furthermore, in cases where the small air space is provided, the opposite glass sheets between the space may become deformed due to wind pressure upon the outer sheet, thus bringing the sheets closer to each other or eventually in contact with each other, which will unavoidably produce the effect of Newton's rings.